Diabetes is one of our most costly diseases in both human and economic terms. The Joslin Diabetes Center T32 Training Program in Diabetes and Metabolism, now entering its 40th year, aims to attract outstanding young scientists into research on diabetes and metabolism, and train them in a vibrant and collaborative environment in which they are exposed to the many facets of diabetes and its causes. The Joslin Diabetes Center, founded in 1898, is a collaborative and integrated organization that fosters cutting-edge research and outstanding diabetes care, and incorporates a strong research base and a busy clinic in a single facility. Its physical and academic infrastructure is greatly enhanced by Joslin having been supported as a Diabetes and Endocrine Research Center (DRC) since 1986. The rich training environment of this T32 Program derives not only from Joslin itself, but also from the many close ties and collaborations that Joslin has with Harvard Medical School and its affiliated hospitals. This T32 Program has trained many outstanding diabetes researchers, including five members of its current Faculty. Our former postdoctoral trainees from the last 15 years have been awarded numerous federal grants (including R01, K99/R00, K08, and F32 awards), and include 25 researchers appointed to the level of Assistant or Associate Professor, mostly at medical schools. Our pre- and post-doctoral trainees from the last 10 years have published 187 training-associated papers in the highest caliber basic and clinical journals. This application aims to build upon this excellence in training. Since the end of 2008 the Joslin T32 program has been directed by T. Keith Blackwell, MD, PhD, an Associate Research Director at Joslin. Our T32 program is supported by Executive, External Advisory, and Fellowship Selection Committees. Our Faculty cover a wide range of interests encompassing Types 1 and 2 diabetes, metabolism, and diabetic complications, and include basic, clinical, and translational scientists. Joslin-affiliated Adjunct Predoctoral trainers provide links between Joslin and other Harvard affiliates. This application requests support for the same number of training positions as currently: five postdoctoral slots and two dedicated Pediatric postdoctoral slots, each awarded for two years, three predoctoral slots awarded for three years each, and eight short-term slots for summer research. The last group includes six slots previously funded as supplements. As currently, we will select MD, MD/PhD, and PhD trainees from Joslin research groups and endocrinology training programs at Harvard-affiliated hospitals, and predoctoral trainees from Harvard PhD programs and other sources. The proposed Program Plan includes many important initiatives in trainee education, enrichment, and advising. These initiatives are designed to strengthen further the training that we offer, bring a diverse group of top young scientists into diabetes research, and promote collaborations among our trainees, Joslin research groups, and other Harvard-affiliated diabetes and metabolism researchers.